Adjustment layers apply effects to everything underneath without affecting individual layers — it’s the cleaner way to grade multiple clips at once.
Steps to use adjustment layers
Go to Layer → New → Adjustment Layer.

Add an effect like Glow, Curves, or Blur to the adjustment layer.

Move or trim the adjustment layer to control exactly where the effect applies in your timeline.

One more thing
Instead of going through the menu, create a new adjustment layer instantly with Ctrl+Alt+Y (Windows) / Command+Option+Y (Mac).
Related how-tos
How to use color grading effects in After Effects
How to add and edit cameras in After Effects
How to add drop shadow in After Effects
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